The present disclosure relates to a valve repair device and a method for repairing a heart valve. More particularly, this disclosure relates to a valve repair device useful in the repair of the mitral valve.
The human heart has four chambers and four one way valves. The right upper chamber, known as the right atrium, receives deoxygenated blood from the body and passes the blood to the right lower chamber, known as the right ventricle, through the tricuspid valve. The blood then passes through the pulmonary valve and is carried via the pulmonary arteries to the lungs for oxygenation. After the blood is oxygenated, it is received into the left side of the heart. The upper chamber, known as the left atrium, receives the blood from the lungs by four pulmonary veins, two from each lung. The blood is then passed to the left ventricle through the mitral valve. The main pumping chamber, the left ventricle, then pushes the blood to the body through the aortic valve.
The mitral valve is also known as a bicuspid valve, as it has two cusps or leaflets. The leaflets consist of the anterior leaflet, which is located adjacent to the aortic valve, and the posterior leaflet. The anterior leaflet is larger than the posterior leaflet. At the junction of the leaflets, each leaflet has a scalloped edge with three rounded portions, known as A1, A2, and A3 for the anterior leaflet, and P1, P2 and P3 for the posterior leaflet. The leaflets are attached to the papillary muscles by the chordae tendineae. The papillary muscles maintain the integrity of chordal leaflet alignment, preventing prolapse of the leaflets. The mitral valve allows blood to flow from the left atrium to the left ventricle but prevents blood from flowing back to the left atrium.
The tricuspid valve and the pulmonary valves are usually less affected by the disease process. Disease in the mitral valve and the aortic valve is more common in the affected adult population.
Mitral valve stenosis, for example, consists of an obstructive lesion to the leaflets of the valve. When the valves are narrow, also called “stenotic” valves, there is an obstruction to the flow of blood to the receiving chamber and an associated back up of blood. Dilatation of the left atrium develops and may be followed by right-sided heart failure and pulmonary edema, causing lung congestion and symptoms of shortness of breath. If the symptoms are severe, surgical intervention may be warranted.
Thickening and calcification is the commonest cause of narrowing of the mitral valve, secondary to the long-term effects of rheumatic disease. The incidence of mitral stenosis has decreased in the United States as the incidence of rheumatic fever has decreased as a result of the early institution of antibiotics. However, the leaking valve or the regurgitant valve incidence has increased in the last two decades. Mitral regurgitation is commonly due to degeneration or myxomatous disease leading to the lack of coaptation of the two mitral leaflets. The lack of coaptation in turn leads to the blood being regurgitated into the left upper chamber or the left atrium, causing pulmonary congestion and shortness of breath. Other causes include rupture of the chordae tendinea or the papillary muscles which are primarily needed to the support the two leaflets. Infection leading to the destruction of the valve leaflet or congenital clefts can also cause mitral regurgitation.
Treatments for these conditions have varied. Opening of the mitral valve was initiated in the 1950's in a closed method, known as a closed commisurotomy (separation of commisures by dialators). With the advent of heart-lung machine in 1955–56 by Dr. John H. Gibbons, Jr., open mitral comrnisurotomy was started with success.
Due to the high recurrence of stenosis, mitral valve replacement with prosthetic valves, typically constructed of a “ball and cage” (or ball valve), became the normal procedure in the 1960's, as proposed by Dr. Albert Starr. These valves were met with limited success as blood flow obstruction occurred with some frequency, leading to thromboembolism, causing strokes. Other attempts to replace the mitral valve were met with limited success. For example, Bjork Shiley valves were introduced as tilting disc valves to decrease the blood flow obstruction, but a flaw in the design led to strut fracture and their discontinuation. St. Jude valves, with a double tilting disc design, were introduced in the late 1970's. These valves have stood the test of durability and acceptable thromboembolism and are the preferred prosthetic valve replacement in the younger population.
Bioprothesis valves, harvested from heterologous mammals, such as swine and bovine, have also been successfully employed, however, such valves frequently wear out due to degeneration and calcification. Moreover, the current designs for the mitral valve are somewhat limited due to the specific VORTEX flow of the left ventricle. U.S. Pat. No. 6,074,417 illustrates a total bioprosthesis mitral valve.
When possible, surgical repair of the defective valve is preferable over the prosthetic replacement. The thrust of surgical repair has been to preserve the integrity of the papillary muscle, the chordae tendineae and the leaflets. Numerous studies have proved this hypothesis in terms of long-term results and the avoidance of anticoagulation, which can cause life-threatening bleeding complications. In the 1980's, Dr. A F Carpentier of France, pioneered several methods to repair the mitral valve. Rupture of the chordae or the prolapse of the middle scallop of the posterior leaflet was easily repaired by excising the diseased piece, repairing the annulas, and suturing the two leaflets. This procedure has become a preferred method and has produced consistent results. These repairs are supported by the placement of a cloth-covered metallic ring to bring the annulus to the near normal level.
Despite the advancement in the surgical management of the posterior leaflet, the repair of the anterior mitral leaflet has proven more difficult. Various surgical techniques have been devised, but without consistent results. Triangular resection of the leaflet, transposing part of the posterior leaflet to the anterior leaflet, chordal shortening have been proposed. Recently the use of the prosthetic material “goretex” sutures have been used as artificial chordae, with some early success. Long Term Results of Mitral Valve Repair for Myxomatous Disease with and without Chordal Replacement with Expanded Polytetrafluoroethylee, The Journal of Thoracic and Cardiovascular Surgery, June 1998, 1279–1286.
The use of prosthetic sutures for the anterior or posterior leaflet requires a great deal of skill on the part of the surgeon to make sure the sutures, duplicating the chords, are of the appropriate length. Moreover, attachment of the sutures to the leaflets and papillary muscles is delicate and cumbersome.